Vehicle tire comprising pneumatic tire inserts

ABSTRACT

A method and article of manufacture is herein disclosed for eliminating the need for pressurized air in a vehicular pneumatic tire. A resilient tubular insert is inserted and carried within a tire casing to simulate pneumatic conditions. The resilient material possesses a longitudinal bore which in combination with a particular range of durometers, enhances the &#34;pneumatic&#34; characteristics of the tire insert. Preferably, the tire insert is discontinuous and is designed to have a diameter greater than the internal diameter of the tire casing under deflated conditions.

This application is a continuation of my copending application Ser. No.003,991 filed Jan. 16, 1979 now U.S. Pat. No. 4,275,782 which in turn isa continuation of my originally-filed application Ser. No. 776,845 filedMar. 14, 1977 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to vehicular tires and particularly to channeledinserts adapted for use in pneumatic tires as a replacement forpressurized air.

One of the major problems associated with pneumatic tires currently inuse is that if the tire is punctured or pierced by a pointed object, thepressurized air contained therein will escape causing the tire todeflate. When this occurs, the tire has absolutely no utility until thepuncture is sealed. This problem is well known to anyone who drives orowns a vehicle and is a particular problem to those who own and/oroperate bicycles having high pressure pneumatic tires as are commonlyfound on the popular ten speed bicycles. Prior to this invention, manytypes of inserts and various methods and techniques have been suggestedas a solution for these problems. One of these is the use of tireinserts. Examples of patents which disclose the use of tire insertsinclude the following U.S. Pat. Nos. 862,785; 918,846; 1,390,467;1,819,632; and 1,506,411.

In each of the above patents, a means is disclosed whereby a rubberinsert is placed within a tire casing to replace pressurized air. Eachof the tubular inserts contains one or more cushioning chambers tosimulate a pressurized pneumatic tire. One of the disadvantages of theinserts hereinbefore disclosed is that during use, the frictionalmovement of the inserts would generate heat and thereby causedeterioration of the tire casing's inner walls. Another problem is thatthere was no convenient means by which the prior art tire inserts couldbe constructed to insure a simulated pressure equivalent to themanufacturer's recommended pressure. In addition, many of the insertsdisclosed in the prior art rely on the use of trapped ambient pressureto obtain a cushioning effect. In so doing, the tire can take on thecharacteristics of a partially flat or an improperly inflated tire whenthe trapped air is released by puncture.

A relatively recent innovation for preventing flat tires proposes amethod for filling a pneumatic tire with a foamed rubber or plasticmaterial and then curing the material within the tire. Upon completingthe curing operation, the tire would be supported by the materialintroduced therein and would not not require pressurized air. The abovetechnique requires special and costly equipment to adapt toconventionally used tires and would not thereby be readily available tothe average consumer.

OBJECTS OF THE INVENTION

To overcome the above disadvantages, it is a primary object of thisinvention to provide a tire insert which can be readily and economicallyinstalled within conventional pneumatic tires.

Still another object of this invention is to provide a tire inserthaving a combination of properties which will simulate a preselectedpneumatic pressure.

Another object of this invention is to provide a pneumatic tire whichwill retain its simulated pneumatic pressure or firmness even whenpierced by sharp objects.

Still another object of this invention is to provide a tire casing whichcan support loads of up to three times its normal capacity.

Another object of this invention is to provide a tire insert which canbe produced in one or more sections yet when placed within a tire casingwill be the equivalent of a continuous tire insert.

SUMMARY OF THE INVENTION

These and other objects of this invention are achieved by a tire insertdesigned to be carried within a pneumatic tire casing mounted on a wheelrim, said tire insert comprising:

(a) a resilient annular member;

(b) having an internal annular bore means dimensioned such that saidbore means defines an empty volume from 0.1444 to 0.3136 of the totalvolume of said member;

(c) said insert having a durometer hardness of between 30 and 65, asmeasured by a Type A Shore Durometer Tester, wherein

(d) if L is the total length of the mean circumference of said annularmember and C is the total length of the mean circumference of saidpneumatic tire casing on said rim, L is larger than C prior to insertionof said insert in said pneumatic tire casing, by an amount between0.005C and 0.013C and wherein

(d) if D is the mean diameter of a cross-section of the resilientannular member, W is the width of the casing at normally inflatedconditions, then D=W=2T whereby said insert is frictionally retainedwithin said pneumatic tire casing against circumferential slidingmovement relative to said tire casing when in use.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a side elevation and cut-away of a conventional bicycletire adopted with a tire insert of this invention.

FIG. 2 is a cross-section of the tire casing and insert taken along line2--2 of FIG. 1.

FIG. 3 is a side elevation of a segmented tire insert.

FIG. 4 is a three-dimensional view of one of the segments used in asegmented tire insert.

FIG. 5 is a three-dimensional view of another embodiment of a segment ofa segmented tire insert.

FIG. 6 is a three-dimensional view of a section of the segment shown inFIG. 5 when positioned within a tire casing.

FIG. 7 is another embodiment of a segmented tire insert having its endsadapted for connection with a correspondingly-mated second segment.

FIG. 8 is a phantom side view of the insert shown in FIG. 7.

FIG. 9 is a three-dimensional view of still another technique forconnecting segmented tire inserts.

FIG. 10 is a sectioned three-dimensional view of a reinforced tireinsert.

FIG. 11 and FIG. 12 are three-dimensional views of still otherembodiments of a tire insert adapted with means for positioning andretaining the inserts within a tire casing.

FIG. 13 is a plug which can be inserted into the stem hole of a tirerim.

FIG. 14 is a graph showing the relationship between durometer, bore sizeand simulated tire pressure.

FIG. 15 is a three-dimensional view of a tire insert having longitudinalsplines.

FIG. 16 is a three-dimensional view of a tire insert having radiallybored openings.

FIG. 17 is a three-dimensional view of a tire insert having wavylongitudinal grooves.

FIG. 18 is a three-dimensional view of a tire insert having spiralledgrooves cut therein.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1, a bicycle wheel, identified generally by thenumeral 10 is shown. The bicycle wheel includes a central hub 12 fromwhich connected spokes 14 emanate radially therefrom to the rim 16.Circumscribed about the rim is a conventional bicycle tire 18 containinga resilient tire insert 20. This embodiment is more clearly depicted inthe cross-section shown in FIG. 2. As shown, the resilient tire insertcontains a central annular bore 22. This central bore functions as acushioning chamber, which in combination with certain physicalcharacteristics of the material from which the insert is constructed,will produce a pneumatic pressure equivalency similar to or identical tothat which would be realized if the tire was filled with pressurizedair.

In FIG. 3, the tire insert 20 is segmented into four equal segments 20a,20b, 20c and 20d respectively. Although the tire insert may becontinuous, the use of three or more segmented sections have been foundto posses certain advantages. For example, the manufacturing andpackaging costs can be substantially reduced without sacrificingoperational quality. FIGS. 7-9 inclusive show a particular technique forconnecting segmented tire inserts if a pseudo-continuous tire insert isdesired. In FIG. 7 the tire insert 30 contains a female end 37 and amale end 34. The male and 34 possesses a reduce diameter extendingmember 36 for fitting into an opening 38 (FIG. 8) bored in the femaleend 37. This relationship is shown in phantom in FIG. 8. In use, themale section 36 is inserted into the opening 38 until the ledge 40 ofthe male end abuts the rim of the female end 37. In FIG. 9 the maleportion 42 of a segmented tire insert 43 is stepped 44 to fit into acorrespondingly molded female or receiving end 46 (shown in phantom) ofa second section of a segmented tire insert 48.

It has been found that if segmented tire inserts are utilized, it ispreferred to have the mean length of the combined segments to beequivalent to the mean circumference of the tire casing underpressurized or expanded conditions. In other words, it has been foundthat the segmented tire inserts should possess a total segmented lengthslightly greater than the circumference of the tire casing when the tirecasing is deflated or at rest. Still more preferably, the length shouldbe equivalent to the length as determined by the following formula:L=C+(a·C) wherein L is the total mean length of the tire insert, C isthe mean circumference of the tire casing and "a" is a decimal numberbetween 0.005 and 0.013 and preferably between 0.007 and 0.011.

As shown in FIG. 4, a tire insert 50 is depicted with a central bore 52.The mean length would be calculated through point 54 if bent to form anarc of a circle. If extended, as shown in FIG. 4, the length throughpoint 54 would be equivalent to the length along its side walls 56. Thelength L of the circumference through 54 is shown by the circular arrowdesigned L in FIG. 3. The mean circumference of the tire casing 60 wouldbe the circumference of the tire casing shown in FIG. 6 as measuredthrough its central point 62. This point will coincide with the centralpoint of the tire insert 64 when the tire inwert is positioned withinthe tire casing 60.

FIG. 5 depicts a particular type of a tire insert which can be used inlieu of the circular tire insert shown in FIG. 4. As depicted in FIG. 5,the tire insert contains, in addition to the centrally bored opening 66,four symmetrically positioned eliptical openings 68a, 68b, 68c and 68drespectively, and four small bore openings 70a, 70b, 70c and 70drespectively. In the alternative, or in addition thereto, as shown inFIG. 6, four small bore openings 70e, 70f, 70g and 70h respectively maybe included. These smaller bored openings and eliptically-shapedopenings can be added if a more stable cushioning effect is desiredunder more stringent and adverse use conditions.

In FIG. 10, a more sophisticated tire insert is depicted wherein thetire insert 80 is reinforced by a webbed matrix 82 and a core 84produced from a material having reinforcing properties.

In FIGS. 11 and 12, a tire insert 90 is shown having a centrally-boredopening 92, a series of eliptically-bored openings 94, and a series ofsmaller bored openings 96. In addition, a pair of curved ledges 98 areprovided to insure correct positioning and alignment of the tire insertabout a tire rim. In FIG. 12, the ledges are replaced by a pair ofconcave grooves 100 for grasping the outer edge of a tire rim (notshown). This arrangement insures positioning and replacement of the tirecasing on the tire rim.

Although the tubular insert normally possesses a smooth, continuousouter surface as shown in FIGS. 3, 4 and 5, variations of the above mayalso be used to advantage. In FIGS. 15-17 inclusive, a number ofvariations are shown.

As shown in FIG. 15, the tubular insert 112 is adapted with a pluralityof longitudinal splines 114 formed by cutting, molding or duringextrusion of the tire insert.

The use of longitudinal splines, or variations thereof, as will besubsequently described in detail, permits the use of rubber or plasticmaterials having a higher durometer. As a general rule, a higherdurometer will produce a tire having a higher pneumatic pressureequivalency. However, the use of higher durometer materials can beoffset or neutralized by utilizing additional openings, cutting,grooves, etc., in the tire insert. The resultis a ride equivalent tothat which could be obtained by using a lower durometer rubber but feweropen area.

In FIG. 16, the tire insert 116 is adapted with openings provided byradial bores 118. In FIGS. 17 and 18, the additional openings in thetire insert 120 and 124 are represented by wavy longitudinal grooves 122and spiraled grooves 126 respectively.

Combinations and variations of the above may also be used if desired.For example, the longitudinal grooves may be cut or bored into theinternal walls of the bore longitudinal opening instead of the outerwalls as depicted in FIG. 15.

One advantage associated with the above approach is that higherdurometer materials may be used in constructing the tire inserts whileat the same time, reducing costs of construction and costs of materialas lesser amounts of high durometer material may be used to achieveessentially identical riding characteristics with that realized by theuse of low durometer materials.

A critical feature of this invention is the use of a tire insert havinga diameter equivalent to the diameter of the tire casing under normallyinflated conditions. This critical diameter can be readily determined bythe use of the following formula, D=W-2T wherein D is the diameter ofthe tire insert, W is the width of the tire casing at normally inflatedconditions and T is the thickness of the side walls of the tire casingunder normally inflated conditions. These relationships are depicted inFIG. 2.

It has been found that if the tire insert is designed such that it doesnot exert a positive outward force against the inner walls of the tirecasing, the tire insert will slidably move within the against the tirecasing during use. This movement can generate frictional heat as well asproduce an uneven and rough ride which, in combination, can incressewear and deterioration of the tire casing.

It has also been found that certain physical properties of the rubber orpolymeric material is critical if a simulated pneumatic condition is tobe achieved. One of the most critical is the hardness of the material asmeasured by the Shore Durometer Testor. The most common type of testorused in the type A durometer which has an indentor point in the shape ofa truncated cone having an 0.631 inch tip diameter and a 0.052 inchdiameter at is shank. The indentor is tapered at an angle of 35° and hasa spring-imposed load of two pounds. The specimen to be tested should beat least 1/4 inch thick. The operator merely places the instrumentagainst the rubber stock to be tested until the bearing plate (throughwhich the indentor works) makes contact with the rubber stock. Thehardness of the rubber stock is indicated by a pointer on a scalemechanically connected to the indentor.

As the hardness of the material is varied, the other physical propertiesof the resilient material will also normally change. For example, themaximum values for tensile strength, resilience, abrasion resistance,tear resistance, etc., occur in rubber or plastic stocks having ahardness in the range of 50-70 durometer.

The tire inserts of this invention may be constructed from a materialhaving a durometer of between about 30 to 65 and preferably from amaterial having a durometer of between about 40 to 50. With materialshaving the above durometer, the volume of the opening or open space willbe less than 0.33 or less than 33% of the total volume of the tireinsert. With the above relationship, the tire insert will provide apneumatic pressure equivalency in a bicycle tire of between about 60-90pounds per square inch.

The materials which may be used to construct the tire insert of thisinvention include most all natural and synthetic rubbers and/orplastic-type polymeric materials having a durometer of between about 30to 65.

Examples of such materials include the following crude and reclaimednatrual and synthetic rubbers: butyl rubber, cyclized rubbers, GRS type(Butadiene-Styrene) rubbers, methyl rubber, neoprene, Nitril rubber(copolymer of butadiene and acrylonitrile), neoprene (soybean rubber),polybutenes, polyester-type rubbers, polyethylene, silicone rubbers,sulfide rubbers, vinyl plastic, polyvinyl chloride, vinyl chloridecopolymers, polyvinyl alcohol and the like.

The tire inserts may be formed by extruding the above types of materialsinto extended lengths and then cutting same to the desired segmentedlengths.

Various types of extruded tubing is commercially available having a wallthickness from 1/32 of an inch to 3/16 of an inch and having an internaldiameter of from between 1/32 to 1 inch. Extruded products having anoutside diameter of up to 2 inches are also readily available. Largerdiameter tubing can generally be obtained on special order.

Where conventional pneumatic tires are used to provide the tire casingfor receiving the tire inserts, caps can be used to fit into the stemopening in the tire rim to prevent water and other contaminants fromentering therein and thereby cause increased deterioration of the tireinsert and casing. A plug 110 typical of those which can be used isshown in FIG. 13.

The relationship between bore diameters, insert length and diameters,material durometer and pneumatic pressure equivalencies have beendetermined. As indicated in Table I below, various simulated tirepressures can be achieved by varying the outer diameter, bore diameterand durometer of the tire insert.

                  TABLE I                                                         ______________________________________                                                                    Insert                                                    Insert     (Inches) Bore                                              Equivalent                                                                            Length     Insert   Diameter Shore A                                  PSI     (Inches)   Diameter (Inches) Durometer                                ______________________________________                                        75      82         1.0      3/8      35/40                                    85      82         1-1/16   3/8      45/50                                    15      82         1.0      3/4      35/40                                    35      82         1-1/16   3/4      45/50                                    75      82         1-1/16   1/2      45/50                                    ______________________________________                                    

It has also been found that, when the tire insert of this invention isto possess a pressure equivalency of about 75 PSI (pressure normallyused with ten speed bicycle tires) there is an approximate 1:1 ratiobetween the durometer and the internal bore of the tire insert. Thisrelationship is particularly meaningful when the tire insert has a oneinch outer diameter. This relationship is shown in Table II below and isdepicted graphically in FIG. 14 of the drawings.

                  TABLE II                                                        ______________________________________                                                 Durometer of Tire       Ratio of                                     Equivalent                                                                             Insert having 1"                                                                            Bore Size Durometer to                                 PSI      Outer Diameter                                                                              In Inches Bore Size                                    ______________________________________                                        75       35            0.38      0.936                                        75       40            0.41      0.985                                        75       45            0.44      1.030                                        75       50            0.47      1.050                                        75       55            0.50      1.100                                        75       60            0.53      1.130                                        75       65            0.56      1.160                                        ______________________________________                                    

As a general rule, it has been found that for each increase in durometerof +5, the bore size, of a one inch O.D. tubular insert, may beincreased by 1/32 of an inch or approximately 0.032 inch. The aboverelationship is valid for durometers of between about 35 and 65.

Since the ratio of the bore cross-sectional area to the totalcross-sectional area indicates the fraction of the empty volume to thetotal volume, for bore sizes ranging from 0.38 inches to 0.56 inches ofthe outside diameter of one inch as in the above table, the ratio ofempty volume to total volume of the inserts may vary from 0.1444 to0.3136.

Where a plurality of bores is used in the tire insert, as opposed to asingle annular bore, the above relationship will remain true if acumulative bore size of the openings is used. Where the bore in the tireinsert is eliptically shaped, an average diameter can be used. Theeliptically-shaped openings in combination with a central bore seem toprovide a more constant cushioning effect and more closely approximatesthe ride that could be realized with air in the pneumatic casingparticularly under more stringent and adverse use conditions.

As the outer diameter of the tire insert is increased, the bore size canlikewise be increased at a constant diameter and a PSI equivalency canbe thereby empirically established or calculated. With the tire insertof this invention, the need for inner tubes or air is avoided. Asexpressed earlier, the tire insert is constructed from an elastic orflexible material having resilient properties. Generally, the insert iscircular in shape. However, a "key hole" shape may be used toaccommodate larger vehicles such as cars, trucks, airplanes, and thelike. The circular tire insert is especially well adapted for use onbicycles or vehicles which would be subjected to less than 1,000 poundstotal weight.

The tire insert may be continuous or one piece with the ends sealed,vulcanized, glued, or otherwise secured or it may be segmented ordiscontinuous. Where the insert is segmented the total diameter or meanlength of the insert is greater than the tire casing at rest. Thisarrangement, as pointed out above, permits the insert to be continuouslyurged outwardly against the inner walls of the tire casing. This avoidsthe insert from sliding about within the casing during use. Although thetire inserts are generally constructed from non-reinforced materials,reinforcing materials such as fibres, cords, metals and the like may beused, if desired. When reinforced materials are used, a reduction intire insert resiliency occurs making its use similar to over-inflatedpneumatic tires.

While this invention has been described with reference to certainspecific embodiments, it should be understood that changes may be madeby one skilled in the art but such changes would not depart from thespirit and scope of this invention which is limited only by the claimsappended hereto.

I claim:
 1. In combination:(a) a wheel rim; (b) a pneumatic tire casingmounted on said wheel rim; and (c) a tire insert, said tire insertcomprising a resilient annular member having an internal annular boremeans dimensioned such that said bore means defines an empty volume from0.1444 to 0.3136 of the total volume of said member, said insert havinga durometer hardness of between 30 to 65 as measured by a type A Shoredurometer testor, wherein if L is the total length of the meancircumference of said annular member and C is the total length of themean circumference of said pneumatic tire casing on said rim, L islarger than C prior to insertion of said insert in said pneumatic tirecasing by an amount between 0.005C and 0.013C and wherein if D is themean diameter of a cross section of the resilient annular member, W thewidth and T the wall thickness of the tire casing under normallyinflated conditions, then D=W-2T whereby said insert is frictionallyretained within said pneumatic tire casing against circumferentialsliding movement relative to said tire casing when in use.
 2. Thecombination of claim 1, in which said resilient annular member issegmented with means formed at the ends of the segments for securingthem in their annular configuration.
 3. The combination according toclaim 2, wherein said means are male and female type connecting meansrespectively.
 4. The combination of claim 3, wherein said male typeconnecting means comprises a reduced diameter extending member and thefemale connecting means includes an opening bored in the end of asegment such that the reduced diameter extending member can be insertedinto the opening.
 5. The combination of claim 3 in which the maleconnecting means constitutes a stepped member and the female connectingmeans includes a correspondingly molded receiving end for receiving saidstepped member.
 6. The combination of claim 2 in which said meansconstitutes sealing the ends together.
 7. The combination of claim 2 inwhich said means constitutes vulcanizing the ends together.
 8. Thecombination of claim 2 in which said means constitutes gluing said endstogether.
 9. The combination of claim 1 in which the tire insert isadapted with longitudinal splines.
 10. The combination of claim 1 inwhich said tire insert is adapted with radial bores.
 11. The combinationof claim 1 including a closure means for closing the stem openingnormally found on said wheel rim.
 12. The combination of claim 11, inwhich said closure means comprises a plug.
 13. The combination of claim1 in which said bore means includes a central bore and symmetricallypositioned eliptical openings and small bore openings about the bore toprovide a more stable cushioning effect under certain adverseconditions.
 14. The combination of claim 1 in which said tire insert isreinforced by a webbed matrix.
 15. The combination of claim 1 in whichsaid tire insert includes a pair of curved ledges to insure correctpositioning and alignment of the tire insert about said wheel rim. 16.The combination of claim 1 in which said tire insert includes a pair ofconcave grooves positioned to engage the outer edge of said tire rim.17. The combination of claim 1 in which said tire insert has a key-holeshape in cross section.
 18. The combination of claim 1 in which saidtire insert is of circular cross section.
 19. The combination of claim1, in which said wheel rim, pneumatic tire casing and tire insert areused on cars.
 20. The combination of claim 1 in which said wheel rim,tire casing and tire insert are used on trucks.
 21. The combination ofclaim 1, in which said wheel rim, tire casing and insert are used onairplanes.
 22. The combination of claim 1, in which said wheel rim, tirecasing and insert are used on bicycles.
 23. The combination of claim 1,in which said wheel rim, tire casing and insert are used on vehicleswhich weigh less than 1,000 pounds.
 24. The combination of claim 1, inwhich the material of said tire insert comprises natural rubber.
 25. Thecombination of claim 1, in which the material of said tire insertcomprises butyl rubber.
 26. The combination of claim 1, in which thematerial of said insert comprises cyclized rubber.
 27. The combinationof claim 1, in which the material of said insert comprisesbutadiene-styrene rubber.
 28. The combination of claim 1, in which thematerial of said insert comprises methyl rubber.
 29. The combination ofclaim 1, in which the material of said insert comprises neoprene. 30.The combination of claim 1, in which the material of said insertcomprises nitril rubber.
 31. The combination of claim 1, in which thematerial of said insert comprises soybean rubber.
 32. The combination ofclaim 1, in which the material of said insert comprises polybutene. 33.The combination of claim 1, in which the material of said insertcomprises polyester-type rubber.
 34. The combination of claim 1, inwhich the material of said insert comprises polyethylene.
 35. Thecombination of claim 1, in which the material of said insert comprisessilicone rubber.
 36. The combination of claim 1, in which the materialof said insert comprises sulfide rubber.
 37. The combination of claim 1,in which the material of said insert comprises vinyl plastic.
 38. Thecombination of claim 1, in which the material of said insert comprisespolyvinyl chloride.
 39. The combination of claim 1, in which thematerial of said insert comprises vinyl chloride copolymers.
 40. Thecombination of claim 1, in which the material of said insert comprisespolyvinyl alcohol.